AIP Conference Proceedings [Author(s) MECHANICS, RESOURCE AND DIAGNOSTICS OF MATERIALS AND STRUCTURES (MRDMS-2018): Proceedings of the 12th International Conference on Mechanics, Resource and Diagnostics of Materials and Structures - Ekaterinburg, Russia (21–25 May 2018)] - The role of permolecular structure in the tribomechanical performance of extrudable polymer components of ultrahigh molecular weight polyethylene